1. Field of the Invention
The present invention generally relates to an electronic endoscope apparatus, and more specifically, to an electronic endoscope apparatus capable of measuring functional information data such as hemoglobin concentration and oxygen saturation hemoglobin, and of indicating this information on a functional image.
2. Description of the Related Art
Recently, research have been directed to relationships between blood flow conditions of submucosa of an organ, e.g., a stomach, and diseases such as gastric ulcer, and many attempts have been made to image functional information such as hemoglobin concentration and oxygen saturation of hemoglobin for diagnostic purposes.
In one conventional electronic endoscope apparatus, when a hemoglobin-concentration distribution image of a biological body is acquired, for instance, an interior portion of a stomach is photographed under lighting conditions of transmission wavelengths of 569 nm (nanometers) and 650 nm, and then a difference is calculated between absorbance values of the two filtered images.
In accordance with the above-described conventional electronic endoscope apparatus, the following difficulties may occur. That is, when the exposure amount of the lighting operation exceeds a certain allowable value, due to movements of the stomach and photographing conditions, either acquired image data, or both image data contain a light intensity over this allowable limit. Namely, even when, for example, the subject (e.g., an interior portion of a stomach) can now be photographed under the optimum exposure value, if this subject will approach the CCD (imaging sensor) of the endoscope apparatus, the subject might be photographed in an over-exposure condition. If the subject is, for instance, the stomach of a biological body, the stomach continuously moves during the endoscopic observation. As a consequence, such an over exposure phenomenon may surely occur. When such a difficulty may be introduced, the calculated difference between the absorbance values of two filtered images may contain an incorrect value, which may result in erroneous functional information of the stomach. Thus, the diagnostic data quality may be deteriorated. Moreover, there is a further problem that no means for recognizing that such incorrect data is employed in the conventional electronic endoscope apparatus. Such electronic endoscope apparatuses are known from, for instance, Japanese KOKAI (Disclosure) patent application No. 58-65138 in 1983.
The present invention has been made in an attempt to solve the above-described problems, and therefore has as an object an electronic endoscope apparatus capable of recognizing to an endoscope operator that an over-exposure region is contained in a functional information image.